A technique relates to forming a chip assembly. Top and bottom chip stack elements containing solder pads and a solder material are provided. Soluble standoffs are applied to the bottom chip stack element. The chip stack elements are aligned to bring the top solder pad in proximity to the bottom solder pad and the temperature is raised to a temperature above the melting temperature of the solder material to form a connected chip assembly. The connected chip assembly is cooled to re-solidify the solder material and soluble standoffs are removed from the connected chip assembly.
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1. A method of assembling a chip system, comprising: providing a top chip stack element having two major surfaces, the top chip stack element comprising a top solder pad on a plane of a first top surface; providing a bottom chip stack element having two major surfaces, the bottom chip stack element comprising a bottom solder pad on a plane of a first bottom surface; providing a solder material on one or more of the top solder pad and the bottom solder pad; applying spherical soluble standoffs to the plane of the first bottom surface, wherein the spherical soluble standoff is a salt; pre-aligning the first chip stack element and the second chip stack element to bring the top solder pad in proximity to the bottom solder pad to form a pre-melt chip assembly; raising the temperature to a temperature above the melting temperature of the solder material to form a connected chip assembly; cooling the connected chip assembly to re-solidify the solder material; and removing the spherical soluble standoffs from the connected chip assembly.
A method for assembling chip systems stacks a top chip with a solder pad over a bottom chip, which also has a solder pad. Solder material is placed on one or both solder pads. Tiny, spherical salt standoffs are applied to the bottom chip's surface. The chips are aligned so the solder pads are close, forming a pre-melt assembly. The assembly is heated above the solder's melting point to connect the chips via the solder. The assembly is then cooled to solidify the solder. Finally, the salt standoffs are removed, leaving a connected chip stack with a controlled gap.
2. The method of claim 1 , further comprising applying a force to the top chip stack element before raising the temperature to a temperature above the melting temperature of the solder material.
The chip assembly method described previously, where chips are stacked using solder and soluble standoffs, includes an extra step: applying force to the top chip *before* heating the solder to its melting point. This ensures good contact between the solder pads when the solder melts, improving the electrical and mechanical connection in the final chip assembly.
3. The method of claim 2 , comprising conducting thermo-compression bonding.
The chip assembly method, involving solder, soluble standoffs, and applied force before heating, uses a specific type of bonding called "thermo-compression bonding". This means the chips are pressed together with heat and force to create a strong connection between the solder pads on the top and bottom chips when the solder melts, before cooling and removing the standoffs.
4. The method of claim 1 , further comprising after removing the soluble standoffs from the connected chip assembly, under filling the connected chip assembly.
After the chips are connected with solder and the salt standoffs are removed, the space between the joined chips is filled with an "underfill" material. This underfill protects the solder joints from stress and environmental factors, improving the chip assembly's reliability and lifespan. The original process includes using solder, spherical soluble standoffs, aligning the chips, heating, cooling, and standoff removal.
5. The method of claim 1 , wherein the soluble standoffs are dispersed in a flux material before applying the spherical soluble standoffs to the plane of the first bottom surface.
Before applying the spherical salt standoffs to the bottom chip surface during chip assembly, the standoffs are mixed into a flux material. The flux helps to clean the solder pad surfaces and promote better solder wetting when the assembly is heated, leading to a more reliable electrical connection, in addition to providing a temporary adhesive to hold the standoffs in place. The original process includes using solder, spherical soluble standoffs, aligning the chips, heating, cooling, and standoff removal.
6. The method of claim 1 , wherein removing the spherical soluble standoffs comprises washing the connected chip assembly with a solvent.
The process of removing the spherical salt standoffs after soldering the chip assembly involves washing the connected chip stack with a solvent. The solvent dissolves the salt material, leaving the desired gap between the chips. The original process includes using solder, spherical soluble standoffs, aligning the chips, heating, cooling, and standoff removal.
7. The method of claim 6 , wherein the solvent is water.
The solvent used to wash away the spherical salt standoffs after chip assembly is water. This is a simple and cost-effective method for removing the standoffs because salts are typically water-soluble. The washing process occurs after the chips are connected using solder and then cooled. The original process includes using solder, spherical soluble standoffs, aligning the chips, heating, cooling, and standoff removal.
8. The method of claim 1 , wherein the salt has a melting temperature greater than or equal to 280° C.
The spherical salt standoffs used in the chip assembly process have a melting temperature of at least 280°C. This ensures they remain solid during the solder reflow process (heating) and maintain the desired gap between the chips until after the solder solidifies. The original process includes using solder, spherical soluble standoffs, aligning the chips, heating, cooling, and standoff removal.
9. The method of claim 8 , wherein the salt has a melting temperature greater than or equal to 400° C.
The spherical salt standoffs used in the chip assembly process have an even higher melting temperature: at least 400°C. This provides a greater margin of safety during the solder reflow process, preventing any deformation or melting of the standoffs that could affect the final chip assembly. The original process includes using solder, spherical soluble standoffs, aligning the chips, heating, cooling, and standoff removal and requires the salt melting point to be above 280°C.
10. The method of claim 1 , wherein the salt is a chloride salt or a sulfate salt.
The type of salt used for the spherical standoffs in chip assembly is either a chloride salt or a sulfate salt. These salts are typically water-soluble, making them easy to remove after the soldering process. The original process includes using solder, spherical soluble standoffs, aligning the chips, heating, cooling, and standoff removal.
11. The method of claim 10 , wherein the salt is sodium chloride, magnesium sulfate, or sodium sulfate.
Specific examples of salts used for the soluble standoffs are sodium chloride (table salt), magnesium sulfate (Epsom salt), or sodium sulfate. These salts are readily available, inexpensive, and easily dissolved in water for removal after the chip assembly process. The original process includes using solder, spherical soluble standoffs, aligning the chips, heating, cooling, and standoff removal. The salts can be either a chloride salt or a sulfate salt.
12. The method of claim 1 , wherein the soluble standoff is a composite coated particle comprising a metal core.
The soluble standoff isn't just a simple salt particle. Instead, it's a more complex particle with a metal core and a coating, which means it's a "composite coated particle". The original process involves applying these standoffs between the top and bottom chip during the soldering assembly. This structure could provide benefits like improved mechanical strength or magnetic properties, while still allowing for removal after soldering. The original process includes using solder, spherical soluble standoffs, aligning the chips, heating, cooling, and standoff removal.
13. The method of claim 12 , wherein the composite coated particle comprises a salt surrounding the metal core.
The composite coated particle, which functions as a soluble standoff during chip assembly, has a salt layer surrounding its metal core. This design combines the structural benefits of a metal core with the solubility of a salt coating, allowing for easy removal after soldering. The original process involves applying these standoffs between the top and bottom chip during the soldering assembly. The original process includes using solder, spherical soluble standoffs, aligning the chips, heating, cooling, and standoff removal.
14. A method of assembling a chip system, comprising: providing a top chip stack element having a top solder pad on a plane of a first top surface; providing a bottom chip stack element having a bottom solder pad on a plane of a first bottom surface; providing a solder material on one or more of the top solder pad and the bottom solder pad; applying composite coated particles to the plane of the first bottom surface, the composite coated particles comprising a metal core; pre-aligning the first chip stack element and the second chip stack element to bring the first solder pad in proximity to the plated solder pad forming a pre-melt chip assembly; compressing the pre-melt chip assembly with a force; forming a connected chip assembly; re-solidifying the solder material; and removing the composite coated particles from the connected chip assembly.
An alternative chip assembly method stacks a top chip with a solder pad over a bottom chip, also with a solder pad. Solder is applied to one or both pads. Composite particles with metal cores are placed on the bottom chip's surface as standoffs. The chips are aligned, forming a pre-melt assembly. The assembly is compressed with force, heated to connect the chips via solder, and then cooled to solidify the solder. Finally, the composite particles are removed.
15. The method according to claim 14 , comprising moving the composite coated particles with a magnetic force.
In the chip assembly method that uses composite particles with metal cores as standoffs, a magnetic force is used to move the particles. The original process involves applying these standoffs between the top and bottom chip during the soldering assembly. The original process includes using solder, composite coated particles, aligning the chips, compressing the pre-melt assembly with force, heating, cooling, and standoff removal.
16. The method according to claim 15 , wherein removing the composite coated particles from the connected chip assembly comprises moving the composite coated particles off of the connected chip assembly with the magnetic force.
The chip assembly method uses composite particles with metal cores as standoffs. Removing the composite particles after the soldering process involves using a magnetic force to physically move the particles *off* of the connected chip assembly. The original process involves applying these standoffs between the top and bottom chip during the soldering assembly. A magnetic force is also used to move the composite coated particles. The original process includes using solder, composite coated particles, aligning the chips, compressing the pre-melt assembly with force, heating, cooling, and standoff removal.
17. A chip assembly, comprising a top chip stack element having two major surfaces, the top chip stack element comprising a top solder pad on a plane of a first top surface; a bottom chip stack element having two major surfaces, the bottom chip stack element comprising a bottom solder pad on a plane of a first bottom surface; a solder material; and a composition comprising a flux material and a soluble standoff.
A finished chip assembly consists of a top chip with a solder pad, a bottom chip with a solder pad, solder connecting the pads, and a composition that contains both flux and a soluble standoff. The flux cleans the solder pads and promotes better solder wetting, while the soluble standoff maintains a controlled gap between the chips.
18. The chip assembly according to claim 17 , wherein the soluble standoff is a composite coated particle comprising a metal core.
In the chip assembly, the soluble standoff within the flux material is a composite coated particle that has a metal core. The structure combines the structural benefits of a metal core with the solubility of the coating, allowing for easy removal during manufacturing. The assembly comprises a top chip with solder, a bottom chip with solder, solder material, a flux material, and a soluble standoff.
19. The chip assembly according to claim 18 , wherein the metal core comprises iron.
The metal core of the composite coated particle, used as a soluble standoff in the chip assembly, is made of iron. The use of iron allows for the particles to be moved by a magnetic force during the manufacturing process. The assembly comprises a top chip with solder, a bottom chip with solder, solder material, a flux material, and a soluble standoff which is a composite coated particle.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
December 15, 2015
June 6, 2017
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